Electromechanical Properties of Polypropylene Blended With Ethylene-Based Elastomers

Polypropylene (PP) is a promising material for the development of power cable insulation due to its excellent dielectric properties. However, the mechanical stiffness of PP is the main concern for power cable extrusion. Therefore, elastomers have been blended with PP to soften the final blends, albeit that this often comes with compromised dielectric properties. In the current work, two ethylene-based elastomers, namely, an ethylene-propylene–diene monomer (EPDM) and an ethylene-octene copolymer (EOC), are blended with a PP homopolymer to tailor PP/elastomer blends with desirable electromechanical properties. The morphology, chemical structure, elongation-at-break, dielectric response, and breakdown strength of the resulting PP/EPDM and PP/EOC blends are analyzed. While the breakdown strength of both the PP/EPDM and PP/EOC blends reduces compared with the pure PP, their breakdown strengths can be comparable to cross-linked polyethylene (XLPE) at a low elastomer content (10 wt.%). Moreover, an improvement in the elongation-at-break of both the PP/EPDM and PP/EOC blends can be achieved. Significantly, the results suggest that PP/EOC systems outperform PP/EPDM blends, especially at high elastomer contents (~30 wt.%). The mechanisms underpinning these property changes are discussed to pave the way for the development of future PP-based power cable insulation materials.